How to put Alert in PHP? [duplicate]

I think this solves:

echo "<script>alert('Mensagem');</script>";

So, being two languages working on different sides, this is the only direct way ...

   //Comando SQL Upadte para Atualizar os dados
     $sql = "UPDATE clientes set nome='$nome',cpf='$cpf',email='$email',setor='$setor',rua='$rua',numero='$numero',telefone='$telefone' WHERE id='$codigo'";
     //Testa o comando SQL
     mysql_query($sql) or die("Não foi possivel exercutar o comando Sql");
     //Mensagem de Sucesso na operação
     echo "O arquivo foi Alterado com sucesso";
     //Fechar a conexão
     mysql_close($conn);
}
else 
{
    echo "<script>alert('não houve conexão com o banco');</script>";
}
?>

It is not very cool to make alerts so it would be more interesting to put this file to be accessed via the ajax request.

The Html form sends via ajax the information to be used in the query, and the php file returns a json as a return to HTML.

By default you can not give an alert in php. Of the ways discussed above work, but I do not think it's interesting.